When to Move the Data Date

I always input the actuals before moving the data date.

you got it right 

input All actuals 

change data date

calculate 

repeate this for every update period

Likewise here, Update Activities then Move the DD.

How to Do this ? ANy Example Please!

you got it right 

determine what date that you wil be recording progress thru. Lets say you wanted to record progress for the month of November.

first copy the existing project

next input All actuals by clikcing on the status tab then if an activity actually started in November check the box next the word started and then put the actual stat date in the box next to the word started if the activitiy also finished in Novemebr then do the same procedure for the finished box.

If an activity started in November but is not yet finished check the box next to the word started and then put the actual start date in the drop down box next to the word started. Now click in the remaing duration box and put in the remining duraiton that it wil take to complete the remainder of the work. 

change data date by pressing the f9 function key and change the date to December 1

click on calculate 

repeate this for every update period